(Clarifies source, adds WWF reaction)
By Peter Jones
KINSHASA, April 23 (Reuters) - British oil company Soco International will start seismic tests this weekend in Democratic Republic of Congo's Lake Edward, an executive said on Wednesday, despite campaigners' attempts to block exploration in a world heritage site.
Conservation group WWF has called on Soco to withdraw from its blocks in UNESCO-protected Virunga national park, saying oil exploration would damage the most bio-diverse park in Africa and is incompatible with its world heritage status.
"The start date for seismic testing has been planned for April 26 and will take about a month," said Roger Cagle, one of Soco's managers in Congo.
Zach Abraham, WWF's global campaigns manager, said Soco was irresponsible for pushing ahead its plans.
"We believe the start of seismic testing shows that Soco intends to exploit oil in Virunga," said Abraham in an emailed statement. "It's impossible to guarantee oil extraction anywhere without pollution, let alone in a place as fragile as this."
In October, WWF made a complaint to the British government, saying Soco's plans to explore in Virunga violated business guidelines laid out by the Organisation for Economic Cooperation and Development (OECD).
In February, the British government's department responsible for overseeing the OECD guidelines offered to mediate between the two parties.
WWF has warned that exploration teams could introduce invasive plant life to the park or disrupt its underground water systems by drilling, with implications for wildlife and habitats.
Soco's Cagle said the company would employ the same seismic surveying company and techniques as London-listed Tullow Oil on the Ugandan side of Lake Albert, around 170 miles (106 miles) north of Lake Edward.
SOCO would also use an environmentally sensitive technique of placing the recorders on the lake bed, Cagle added.
Congo's environment and oil ministers have said they wished to establish the value of the oil in Virunga before deciding whether to exploit it. WWF argues the park is worth more to Congo as a world heritage site than as an oil source.
The poverty-stricken country - whose development has been hindered by mismanagement, corruption and violence - is aiming to increase oil production from just 25,000 barrels per day by exploiting reserves under its soil in the east and offshore in the west. (Reporting By Peter Jones; Editing by Daniel Flynn and David Evans)